1. Field of Use
This invention relates generally to forage harvester machines used in agriculture to cut or chop severed crop material into small pieces and, in particular, to electrical control systems for the drive mechanisms employed in such machines.
2. Description of the Prior Art
One type of prior art tractor-propelled and powered forage harvester machine comprises a feed roll mechanism comprising one or more pairs of rollers for receiving severed crop material and for delivering the material to a rotary cutterhead mechanism which cuts or chops it into small pieces for delivery to a blower which discharges the pieces into a forage wagon behind the harvester. A drive means on the harvester is connectable to the tractor PTO for rotatably driving a rotatable blade element in the cutterhead mechanism. A drive mechanism is provided on the harvester for delivering motive power from the cutterhead mechanism (or from the drive means therefor) to operate the feed roll mechanism. The rotatable elements in the cutterhead mechanism and in the blower are rotatably driven in one direction only, whereas the drive mechanism includes components operable to enable the feed rolls in the feed roll mechanism to be driven forward for normal delivery, to be stopped in case of crop jamming or entry of foreign material therein, or to be driven in reverse to relieve the jamming or dislodge the foreign material. In some prior art drive mechanisms such components include electrically operable clutches which are controlled by selector switches. U.S. Pat. No. 4,049,207 discloses a forage harvester drive mechanism which includes a pair of alternatively engageable electric clutches which are energizable and de-energizable in response to actuation of manually operable electric switches for effecting forward or reverse operation or stoppage of the feed rolls. Prior art forage harvesters, whether employing manually or electrically operable directional control clutches, typically use breakable and replaceable shear pins at one or more locations in the drive mechanism to sever the drive connection to the feed rolls in the event that serious feed roll jamming occurs to thereby prevent mechanical damage to the machine. Prior art forage harvesters of the aforesaid character are relatively complex as regards the construction and mode of operation of the drive mechanism, including the clutches therein, and are relatively costly to manufacture and difficult to maintain and repair. Furthermore, replacement of broken shear pins very often requires partial disassembly of components and is time-consuming and impedes agricultural operations.
The following six (6) U.S. patents illustrate the state of the art: U.S. Pat.Nos. 3,739,559; 3,732,740; 3,523,411; 3,444,673; 3,999,674; and 4,174,072.